Method and system for controlling heat pump water heater

ABSTRACT

The present disclosure provides a method and a system for controlling a heat pump water heater. The method includes: receiving a turn-on instruction; detecting the current temperature of the water in the water tank and the ambient temperature; acquiring a turn-on temperature difference according to the set temperature of the heat pump water heater and the ambient temperature, and acquiring a turn-on threshold according to the turn-on temperature difference; determining whether the current temperature is less than the turn-on threshold; if no, maintaining the current state; and if yes, controlling to enable the heat pump system to heat the water in the water tank.

PRIORITY INFORMATION

This application is based upon and claims a priority to Chinese Patent Application Serial No. 201410773884.4, filed with the State Intellectual Property Office of P. R. China on Dec. 12, 2014, the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure relates to the technology field of household appliances, and more particularly, to a method and a system for controlling a heat pump water heater and a heat pump water heater.

BACKGROUND

At present, a heat pump water heater is generally turned on as follows. By setting a turn-on temperature difference, a heat pump is turned on when an actual water temperature is lower than a difference between a set temperature and the turn-on temperature difference, and otherwise the heat pump is remained in the current state. Currently, the turn-on temperature difference is fixed. A turn-on condition is simple by adopting the fixed turn-on temperature difference, so that the turn-on time may be determined visually according to the temperature. However, when the ambient temperature is high, heating capacity is great. In such a case, if the turn-on temperature difference is small, a main engine is turned on and off frequently and an operation load is too high, thereby affecting reliability of the heat pump system and wasting large amounts of energy. When the ambient temperature is low, the heating capacity is small. In such a case, adopting the fixed turn-on temperature difference may cause a delayed turn-on, and requirements of using hot water may not be satisfied, thereby causing poor comfort. When the set temperature is high, the fixed turn-on temperature difference may lead to that the heat pump system is always running under high load conditions, thereby seriously affecting the reliability of the heat pump system.

SUMMARY

The present disclosure aims to solve at least one of the problems existing in the related art to some extent. To this end, objective of a first aspect of the present disclosure is to provide a method for controlling a heat pump water heater, which can control a turn-on of the heat pump water heater intelligently.

An objective of a second aspect of the present disclosure is to provide a system for controlling a heat pump water heater.

In order to realize the above objectives, a method for controlling a heat pump water heater according to embodiments of the first aspect of the present disclosure includes: receiving a turn-on instruction; detecting an ambient temperature and a current water temperature in a water tank of the heat pump water heater; acquiring a turn-on temperature difference according to the ambient temperature and a set temperature of the heat pump water heater, and acquiring a turn-on threshold according to the turn-on temperature difference; and determining whether the current water temperature is less than the turn-on threshold, keeping a current state if the current water temperature is greater than or equal to the turn-on threshold, and controlling the heat pump system to turn on so as to heat the water in the water tank if the current water temperature is less than the turn-on threshold.

With the method for controlling a heat pump water heater according to embodiments of the present disclosure, the turn-on temperature difference is acquired according to the ambient temperature and the set temperature, and the turn-on threshold is determined intelligently according to the turn-on temperature difference, thereby improving comfort of the user when using the water, improving the user experience and ensuring the reliability of the heat pump system.

In an embodiment of the present disclosure, the turn-on temperature difference is acquired according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature.

In an embodiment of the present disclosure, the turn-on temperature difference is acquired according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature, in which the higher the ambient temperature is, the greater the corrected temperature corresponding to the ambient temperature is; and the higher the set temperature is, the greater the corrected temperature corresponding to the set temperature is.

In an embodiment of the present disclosure, the turn-on threshold is a difference between the set temperature and the turn-on temperature difference.

In an embodiment of the present disclosure, the turn-on threshold is a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.

In an embodiment of the present disclosure, the turn-on threshold is a minimum of a difference between the set temperature and the turn-on temperature difference and a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.

A system for controlling a heat pump water heater according to embodiments of the second aspect of the present disclosure includes a heat pump system and a controller. The controller includes a receiving module, a temperature sensing module and a processor. The receiving module is configured to receive a turn-on instruction. The temperature sensing module is configured to detect an ambient temperature and a current water temperature in a water tank of the heat pump water heater. The processor is configured to acquire a turn-on temperature difference according to the ambient temperature and a set temperature of the heat pump water heater, and to acquire a turn-on threshold according to the turn-on temperature difference; the processor is further configured to determine whether the current water temperature is less than the turn-on threshold, to keep a current state if the current water temperature is greater than or equal to the turn-on threshold, and to control the heat pump system to turn on and to heat the water in the water tank if the current water temperature is less than the turn-on threshold.

With the system for controlling a heat pump water heater according to embodiments of the present disclosure, the processor acquires the turn-on temperature difference according to the ambient temperature and set temperature acquired by the temperature sensing module, and determines the turn-on threshold according to the turn-on temperature difference intelligently, thereby improving comfort of the user when using the water, improving the user experience and ensuring the reliability of the heat pump system.

In an embodiment of the present disclosure, the processor is further configured to acquire the turn-on temperature difference according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature.

In an embodiment of the present disclosure, the processor is further configured to acquire the turn-on temperature difference according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature, in which the higher the ambient temperature is, the greater the corrected temperature corresponding to the ambient temperature is; and the higher the set temperature is, the greater the corrected temperature corresponding to the set temperature is.

In an embodiment of the present disclosure, the turn-on threshold is a difference between the set temperature and the turn-on temperature difference.

In an embodiment of the present disclosure, the turn-on threshold is a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.

In an embodiment of the present disclosure, the turn-on threshold is a minimum of a difference between the set temperature and the turn-on temperature difference and a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.

Additional aspects and advantages of embodiments of present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing a method for controlling a heat pump water heater according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram illustrating a relationship between an ambient temperature and a corrected temperature thereof according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram illustrating a relationship between a set temperature and a corrected temperature thereof according to an embodiment of the present disclosure; and

FIG. 4 is a block diagram illustrating a system for controlling a heat pump water heater according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

In the description of the present disclosure, it should be understood that, terms such as “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “over”, “below”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “in”, “out”, “clockwise”, “anti-clockwise”, “axial”, “radial” and “circumference” refer to the directions and location relations which are the directions and location relations shown in the drawings, and for describing the present disclosure and for describing in simple, and which are not intended to indicate or imply that the device or the elements are disposed to locate at the specific directions or are structured and performed in the specific directions, which could not to be understood to the limitation of the present disclosure.

In addition, terms “first” and “second” are merely used for explanation, and should not understood to indicate or imply relative importance or implicitly specify the number of features indicated. Therefore, a feature defined with “first” or “second” may explicitly or implicitly include at least one of the feature. In the specification, “a plurality of” refers to at least two, for example, two or three, unless otherwise defined explicitly.

In the description of the present disclosure, unless specified or limited otherwise, the terms “mounted,” “connected,” “coupled,” and “fixed” and variations thereof are used broadly and encompass such as fixed or detachable mountings, connections and couplings, and can be mechanical or electrical mountings, connections and couplings, and also can be direct and via media indirect mountings, connections, and couplings, and further can be inner mountings, connections and couplings of two components or interaction relations between two components, unless otherwise specified, which can be understood by those skilled in the art according to the detail embodiment of the present disclosure.

In the description of the present disclosure, unless specified or limited otherwise, the first characteristic is “on” or “under” the second characteristic refers to the first characteristic and the second characteristic can be direct or via media indirect mountings, connections, and couplings. And, the first characteristic is “on”, “above”, “over” the second characteristic may refer to the first characteristic is right over the second characteristic or is diagonal above the second characteristic, or just refer to the horizontal height of the first characteristic is higher than the horizontal height of the second characteristic. The first characteristic is “below” or “under” the second characteristic may refer to the first characteristic is right over the second characteristic or is diagonal under the second characteristic, or just refer to the horizontal height of the first characteristic is lower than the horizontal height of the second characteristic.

Reference will be made in detail to embodiments of the present disclosure. The exemplary embodiments are shown in the accompanying drawings, in which the same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. The embodiments described herein with reference to accompanying drawings are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure.

Referring to FIG. 1, a method for controlling a heat pump water heater according to an embodiment of the first aspect of the present disclosure is configured to control a heat pump system of the heat pump water heater to turn on for heating water in a water tank, and includes: receiving a turn-on instruction; detecting an ambient temperature and a current water temperature in the water tank; acquiring a turn-on temperature difference according to the ambient temperature and a set temperature of the heat pump water heater, and acquiring a turn-on threshold according to the turn-on temperature difference; and determining whether the current water temperature is less than the turn-on threshold, keeping a current state if the current water temperature is greater than or equal to the turn-on threshold, and controlling the heat pump system to turn on and to heat the water in the water tank if the current water temperature is less than the turn-on threshold. The specific implementation procedures may be as follows.

Block S1, a turn-on instruction is received.

Block S2, an ambient temperature and a current water temperature in the water tank are detected.

In an embodiment of the present disclosure, the ambient temperature and the current water temperature in the water tank of the heat pump water heater are detected by a temperature sensing module.

Block S3, a turn-on temperature difference is acquired according to the ambient temperature and a set temperature of the heat pump water heater, and a turn-on threshold is acquired according to the turn-on temperature difference.

Block S4, it is determined whether the current water temperature is less than the turn-on threshold, a current state is kept if the current water temperature is greater than or equal to the turn-on threshold, and the heat pump system is controlled to turn on and to heat the water in the water tank if the current water temperature is less than the turn-on threshold.

In an embodiment of the present disclosure, the turn-on temperature difference ΔT is acquired according to the ambient temperature T₄ and the set temperature T_(s) of the heat pump water heater. The turn-on temperature difference ΔT is determined by a formula of ΔT=f(T₄, T_(s))=e^(lg(T) ⁴ ¹⁵⁾+10 ln(T_(s)/45).

For example, ΔT is computed according to T₄ and T_(s) as follows.

A corrected temperature corresponding to the ambient temperature T₄ is computed according to a formula of e^(lg(T) ⁴ ⁺¹⁵⁾, which may be shown as following table.

T₄ (° C.) −10 −6 −2 2 6 10 14 18 22 26 30 34 38 42 46 50 e^(lg(T) ⁴ ⁺¹⁵⁾ (° C.) 2 3 3 3 4 4 4 5 5 5 5 5 6 6 6 6

A corrected temperature corresponding to the set temperature T_(s) is computed according to a formula of 10 ln(T_(s)/45), which may be shown as following table.

T_(s) (° C.) 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 10ln(T_(s)/45) (° C.) −1 −1 0 0 1 1 1 2 2 3 3 3 4 4 4 4

Examples are taken to illustrate the computing procedure of ΔT.

Example One: when the ambient temperature T₄ is 14° C., and the set temperature T_(s) is 42° C., the corresponding turn-on temperature difference ΔT may be as follows.

According to the above tables, the value corresponding to T₄ is 4 when the ambient temperature T₄ is 14° C., and the value corresponding to T_(s) is −1 when the set temperature T_(s) is 42° C. Then, a value of ΔT may be as ΔT=4+ (−1)=4−1=3. That is, the turn-on temperature difference ΔT=3° C. when the ambient temperature T₄ is 14° C. and the set temperature T_(s) is 42° C.

In an embodiment of the present disclosure, the turn-on threshold T is a difference of the set temperature T_(s) and the turn-on temperature difference ΔT. That is, T=T_(s)−ΔT=39° C. When it is detected that in the water tank, the current water temperature T₁<39° C., the heat pump system is controlled to be turned on to perform heating. In addition, the fixed temperature difference currently adopted is 5° C. or 6° C., so that the turn-on may be realized in advance when ΔT=3° C., thereby ensuring the timeliness and comfort of using water by the user.

Example Two: when the ambient temperature T₄ is 14° C., and the set temperature T_(s) is 60° C., the corresponding turn-on temperature difference ΔT may be as follows.

According to the above tables, the value corresponding to T₄ is 4° C. when the ambient temperature T₄ is 14° C., and the value corresponding to T_(s) is 3° C. when the set temperature T_(s) is 60° C. Then, a value of ΔT may be as ΔT=4+3=7° C. That is, the turn-on temperature difference ΔT=7° C. when the ambient temperature T₄ is 14° C. and the set temperature T_(s) is 60° C.

In an embodiment of the present disclosure, the turn-on threshold T is the difference of the set temperature T_(s) and the turn-on temperature difference ΔT. That is, T=T_(s)−ΔT=53° C. When it is detected that in the water tank, the current water temperature T₁<53° C., the heat pump system is controlled to be turned on to heat the water in the water tank. In addition, the fixed temperature difference currently adopted is 5° C. or 6° C., so that the delayed turn-on may be realized when ΔT=7° C., thereby reducing the heat pump system operating under high load and ensuring the reliability.

In another embodiment of the present disclosure, the turn-on temperature difference ΔT is acquired according to a corrected temperature ΔT₄ corresponding to the ambient temperature T₄ and a corrected temperature ΔT_(s) corresponding to the set temperature T_(s). The turn-on temperature difference ΔT is determined by a formula of ΔT=f(ΔT₄, ΔT_(s))=ΔT₄+ΔT_(s).

Generally, the higher the ambient temperature T₄ is, the more energy absorbed from the outside by refrigerant is. In order to avoid turning on or off the heat bump system frequently, the corrected temperature ΔT₄ may be set according to the ambient temperature T₄. In addition, since the user's body temperature is generally around 37° C., the corrected temperature ΔT_(s) may be set according to the set temperature T_(s), so as to ensure the comfort of the user when using the water. For example, when the set temperature T_(s) is greater than 40° C., the water temperature in the heat bump water heater is kept close to the level of the user's body temperature by setting the corrected temperature ΔT_(s). ΔT₄ and ΔT_(s) are set according to specific conditions, such as a volume of the water tank.

For example, ΔT₄ is determined by searching FIG. 2. In FIG. 2, in a certain temperature range, the corrected temperature ΔT₄ corresponding to the ambient temperature T₄ is a certain value, for example, when 7<T₄<18, ΔT₄=5° C. Generally, with the increase of the ambient temperature T₄, the corrected temperature ΔT₄ shows the tendency of increase. Similarly, ΔT_(s) is determined according to FIG. 3, in a certain temperature range, the corrected temperature ΔT_(s) corresponding to the set temperature T_(s) is a certain value, for example, when 55 <T_(s)<60, ΔT_(s)=2° C. Generally, with the increase of the set temperature T_(s), the corrected temperature ΔT_(s) shows the tendency of increase. Examples are taken to illustrate the computing procedure of ΔT.

Example One: when the ambient temperature T₄ is 14° C., and the set temperature T_(s) is 42° C., the corresponding turn-on temperature difference ΔT may be as follows. According to FIG. 2 and FIG. 3, the corrected temperature ΔT₄ corresponding to T₄ is 5° C. when the ambient temperature T₄ is 14° C., and the corrected temperature ΔT_(s) corresponding to T_(s) is −1° C. when the set temperature T_(s) is 42° C. Then, a value of ΔT may be as ΔT=5+ (−1)=5−1=4° C. That is, the turn-on temperature difference ΔT=4° C. when the ambient temperature T₄ is 14° C. and the set temperature T_(s) is 42° C.

In an embodiment of the present disclosure, the turn-on threshold T is the difference of the set temperature T_(s) and the turn-on temperature difference ΔT. That is, T=T_(s)−ΔT=38° C. When it is detected that in the water tank, the current water temperature T₁<38° C., the heat pump system is controlled to be turned on to perform heating. In addition, the fixed temperature difference currently adopted is 5° C. or 6° C., so that the turn-on may be realized in advance when ΔT=4° C., thereby ensuring the timeliness and comfort of using water by the user.

Example Two: when the ambient temperature T₄ is 14° C., and the set temperature T_(s) is 60° C., the turn-on temperature difference ΔT may be as follows.

According to FIG. 2 and FIG. 3, the corrected temperature corresponding to T₄ is 5° C. when the ambient temperature T₄ is 14° C., and the corrected temperature corresponding to T_(s) is 3° C. when the set temperature T_(s) is 60° C. Then, a value of ΔT may be as ΔT=5+3=8° C. That is, the turn-on temperature difference ΔT=8° C. when the ambient temperature T₄ is 14° C. and the set temperature T_(s) is 60° C.

In an embodiment of the present disclosure, the turn-on threshold T is the difference of the set temperature T_(s) and the turn-on temperature difference ΔT, that is, T=T_(s)−ΔT=52° C. When it is detected that in the water tank, the current water temperature T₁<52° C., the heat pump system is controlled to be turned on to heat the water in the water tank. In addition, the fixed temperature difference currently adopted is 5° C. or 6° C., so that the delayed turn-on may be realized when ΔT=8° C., thereby reducing the heat pump system operating under high load and ensuring the reliability.

In another embodiment of the present disclosure, the turn-on temperature difference ΔT is determined by a formula of

ΔT=f(a, b, c_ΔT ₄ , c_ΔT ₄ , c_ΔT _(s))=[a□c_ΔT ₄ +b□c_ΔT _(s)],

where a is a weight corresponding to the ambient temperature T₄, b is a weight corresponding to the set temperature T_(s), c_ΔT ₄ is the corrected temperature corresponding to the ambient temperature T₄, and the higher the ambient temperature T₄ is, the greater the corresponding corrected temperature c_ΔT₄ is. c_ΔT_(s) is the corrected temperature corresponding to the set temperature T_(s), and the higher the set temperature T_(s) is, the greater the corresponding corrected temperature c_ΔT_(s) is. [ ] is a rounding operator.

For example, in an embodiment of the present disclosure, a is set to 4, b is set to 4, parameter values of c_ΔT₄ and c_ΔT_(s) may be shown in the following tables. The value of c_ΔT₄ may be acquired according to the following rule: when T₄₁<T₄<T₄₂, the value of c_ΔT₄ is the corrected temperature corresponding to T₄₁, in which T₄₁ and T₄₂ are adjacent ambient temperatures shown in the table, and T₄ is the current ambient temperature. For example, when the current ambient temperature T₄=8° C., T₄ is between T₄₁=6° C. and T₄₂=10° C., and thus c_ΔT₄=0.9° C., that is the corrected temperature c_ΔT₄ corresponding to T₄₁. Similarly, the value of c_ΔT_(s) may be acquired according to the following rule: when T_(s1)<T_(s)<T _(s2), the value of c_ΔT_(s) is the corrected temperature corresponding to T_(s1), in which T_(s1) and T_(s2) are adjacent set temperatures shown in the table. For example, when the current set temperature T_(s)=43° C., T_(s) is between T_(s1)=42° C. and T_(s2)=44° C., and thus c_ΔT=−0.2° C. (that is the corrected temperature c_ΔT_(s) corresponding to T_(s1)).

T₄ −10 −6 −2 2 6 10 14 18 22 26 30 34 38 42 46 50 c_ΔT₄ 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0

T_(s) 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 c_ΔTs −0.3 −0.2 −0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Examples are taken to illustrate the computing procedure of ΔT.

Example One: when the ambient temperature T₄ is 14° C., and the set temperature T_(s) is 42° C., the turn-on temperature difference ΔT may be as follows. According to the above table, c_ΔT₄ corresponding to T₄ is 1.1° C. when the ambient temperature T₄ is 14° C. and c_ΔT_(s) corresponding to T_(s) is −0.2° C. when the set temperature T_(s) is 42° C. Then, the value of ΔT may be as follows: ΔT=[4*1.1+4* (−0.2)]=[3.6]=3° C. That is, the turn-on temperature difference ΔT=3° C. when the ambient temperature T₄ is 14° C. and the set temperature T_(s) is 42° C.

In an embodiment of the present disclosure, the turn-on threshold T is the difference of the set temperature T_(s) and the turn-on temperature difference ΔT. That is, T=T_(s)−ΔT=39° C. When it is detected that in the water tank, the current water temperature T₁<39° C., the heat pump system is controlled to be turned on to perform heating. In addition, the fixed temperature difference currently adopted is 5° C. or 6° C., so that the turn-on may be realized in advance when ΔT=3° C., thereby ensuring the timeliness and comfort of using water by the user.

Example Two: if the ambient temperature T₄ is 14° C., and the set temperature T_(s) is 60° C., the turn-on temperature difference ΔT may be as follows. According to the above table, c_ΔT₄ corresponding to T₄ is 1.1° C. when the ambient temperature T₄ is 14° C. and c_ΔT_(s) corresponding to T_(s) is 0.7° C. when the set temperature T_(s) is 60° C. Then, the value of ΔT may be as follows: ΔT=[4*1.1+4*0.7]=[7.2]=7° C. That is, the turn-on temperature difference ΔT=7° C. when the ambient temperature T₄ is 14° C. and the set temperature T_(s) is 60° C.

In an embodiment of the present disclosure, the turn-on threshold T is the difference of the set temperature T_(s) and the turn-on temperature difference ΔT. That is, T=T_(s)−ΔT=53° C. When it is detected that in the water tank, the current water temperature T₁<53° C., the heat pump system is controlled to be turned on to heat the water in the water tank. In addition, the fixed temperature difference currently adopted is 5° C. or 6° C., so that the delayed turn-on may be realized when ΔT=7° C., thereby reducing the heat pump system operating under high load and ensuring the reliability.

In another embodiment of the present disclosure, the turn-on threshold T is a difference between a turn-off temperature T_(off) and the turn-on temperature difference ΔT, and the turn-off temperature T_(off) is a limit temperature reached by the water heated by the heat pump system. That is, T=T_(off)−ΔT. This reduces the load on the heat pump system, and ensures the reliability of the heat pump system.

In still another embodiment of the present disclosure, the turn-on threshold T is a minimum of a difference between the set temperature T_(s) and the turn-on temperature difference ΔT and a difference between a turn-off temperature T_(off) and the turn-on temperature difference ΔT. That is, T=min(T_(s)−ΔT, T_(off)−ΔT). Similarly, this reduces the load on the heat pump system, and ensures the reliability of the heat pump system.

With the method for controlling a heat pump water heater according to embodiments of the present disclosure, the turn-on temperature difference is acquired according to the ambient temperature and the set temperature, and the turn-on threshold is determined intelligently according to the turn-on temperature difference, thereby improving comfort of using the water by the user, improving the user experience and ensuring the reliability of the heat pump system.

The system 100 according to embodiments of the second aspect, as shown in FIG. 4, includes a heat pump system 10 and a controller 20. The controller 20 includes a receiving module 22, a temperature sensing module 24 and a processor 26.

The receiving module 22 is configured to receive a turn-on instruction. The temperature sensing module 24 includes a first temperature sensor 242 and a second temperature sensor 244.

The first temperature sensor 242 is configured to detect a current water temperature in a water tank of the heat pump water heater. The second temperature sensor 244 is configured to detect an ambient temperature. The processor 26 is configured to acquire a turn-on temperature difference according to the ambient temperature and a set temperature of the heat pump water heater, and to acquire a turn-on threshold according to the turn-on temperature difference. The processor 26 is further configured to determine whether the current water temperature is less than the turn-on threshold, to keep a current state if the current water temperature is greater than or equal to the turn-on threshold, and to control the heat pump system 10 to turn on and to heat the water in the water tank if the current water temperature is less than the turn-on threshold.

With the system for controlling a heat pump water heater according to embodiments of the present disclosure, the processor acquires the turn-on temperature difference according to the ambient temperature and set temperature acquired by the temperature sensing module, and determines intelligently the turn-on threshold according to the turn-on temperature difference, thereby improving comfort of using the water by the user, improving the user experience and ensuring the reliability of the heat pump system.

It should be noted that, specific implementation manners of the system for controlling a heat pump water heater according to embodiments of the present disclosure may be similar to these of the method, and reference may be made to the description of the method, which is not repeated herein in order to reduce redundancy.

Reference throughout this specification to “an embodiment,” “some embodiments,” “one embodiment”, “another example,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment”, “in an embodiment”, “in another example,” “in an example,” “in a specific example,” or “in some examples,” in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from scope of the present disclosure. 

1. A method for controlling a heat pump water heater, comprising: receiving a turn-on instruction; detecting an ambient temperature and a current water temperature in a water tank of the heat pump water heater; acquiring a turn-on temperature difference according to the ambient temperature and a set temperature of the heat pump water heater, and acquiring a turn-on threshold according to the turn-on temperature difference; and determining whether the current water temperature is less than the turn-on threshold, keeping a current state if the current water temperature is greater than or equal to the turn-on threshold, and controlling the heat pump system to turn on and to heat the water in the water tank if the current water temperature is less than the turn-on threshold.
 2. The method according to claim 1, wherein the turn-on temperature difference is acquired according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature.
 3. The method according to claim 1, wherein the turn-on temperature difference is acquired according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature, in which the higher the ambient temperature is, the greater the corrected temperature corresponding to the ambient temperature is; and the higher the set temperature is, the greater the corrected temperature corresponding to the set temperature is.
 4. The method according to claim 1, wherein the turn-on threshold is a difference between the set temperature and the turn-on temperature difference.
 5. The method according to claim 1, wherein the turn-on threshold is a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.
 6. The method according to claim 1, wherein the turn-on threshold is a minimum of a difference between the set temperature and the turn-on temperature difference and a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.
 7. A system for controlling a heat pump water heater, comprising: a heat pump system; a controller, comprising: a receiving module, configured to receive a turn-on instruction; a temperature sensing module, configured to detect an ambient temperature and a current water temperature in the heat pump water heater; and a processor, configured to acquire a turn-on temperature difference according to the ambient temperature and a set temperature of the heat pump water heater, and to acquire a turn-on threshold according to the turn-on temperature difference, wherein the processor is further configured to determine whether the current water temperature is less than the turn-on threshold, to keep a current state if the current water temperature is greater than or equal to the turn-on threshold, and to control the heat pump system to turn on and to heat water in the heat pump water heater if the current water temperature is less than the turn-on threshold.
 8. The system according to claim 7, wherein the processor is further configured to acquire the turn-on temperature difference according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature.
 9. The system according to claim 7, wherein the processor is further configured to acquire the turn-on temperature difference according to a corrected temperature corresponding to the ambient temperature and a corrected temperature corresponding to the set temperature, wherein the higher the ambient temperature is, the greater the corrected temperature corresponding to the ambient temperature is; and the higher the set temperature is, the greater the corrected temperature corresponding to the set temperature is.
 10. The system according to claim 7, wherein the turn-on threshold is a difference between the set temperature and the turn-on temperature difference.
 11. The system according to claim 7, wherein the turn-on threshold is a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.
 12. The system according to claim 7, wherein the turn-on threshold is a minimum of a difference between the set temperature and the turn-on temperature difference and a difference between a turn-off temperature and the turn-on temperature difference, and the turn-off temperature is a limit temperature reached by the water heated by the heat pump system.
 13. The system according to claim 7, wherein the temperature sensing module comprises: a first temperature sensor, configured to detect the current water temperature in a water tank of the heat pump water heater; and a second temperature sensor, configured to detect the ambient temperature. 